1) Field of the Invention
This invention generally relates to the devices and methods for the fabrication of semiconductor devices, and more particularly to the fabrication of Field Effect Transistors (FETs) having embedded Source/Drain regions with controlled impurity profiles.
2) Description of the Prior Art
It is now well-known that SiGe can be embedded into the source/drain (S/D) regions of PFETs to generate uniaxial stress in the silicon channel. This in turn increases the carrier mobility in the PFET channel and thus enhances the PFET device performance significantly. However, the integration of embedded SiGe (eSiGe) into the normal CMOS process flow is extremely challenging. The extent of performance enhancement also depends strongly on the stress generated by the SiGe itself, the active dopant concentration in the eSiGe and the proximity of the stressor to the channel region.
The importance of overcoming the various deficiencies noted above is evidenced by the extensive technological development directed to the subject, as documented by the relevant patent and technical literature. The closest and apparently more relevant technical developments in the patent literature can be gleaned by considering the following.
U.S. Pat. No. 6,921,913: Strained-channel transistor structure with lattice-mismatched zone—Strained-channel transistor structure includes portions of source and drain regions adjacent to strained channel region and lattice mismatched with respect to channel region. Inventor: Yeo, Yee-Chia; Singapore, Singapore
U.S. Pat. No. 5,442,205: Semiconductor heterostructure devices with strained semiconductor layers—Semiconductor heterostructure devices with strained semiconductor layers—have monocrystalline silicon substrate, spatially graded epitaxial layer of germanium-silicon, spatially ungraded layers of germanium-silicon and epitaxial layer of germanium or silicon. Inventor: Brasen, Daniel.
U.S. Pat. No. 6,831,292 and US20050054168A1: Semiconductor structures employing strained material layers with defined impurity gradients and methods for fabricating same—Semiconductor structure has strained layer(s) with specified impurity gradient. Inventor: Currie, Matthew; et al.
U.S. Pat. No. 6,844,227: Semiconductor devices and method for manufacturing the same—Field effect transistor includes a channel layer whose thickness is a critical film thickness or less so that dislocation due to strain may not be caused depending on the carbon content. Inventor: Kubo, Minoru; Mie, Japan
US20040262694A1: Transistor device containing carbon doped silicon in a recess next to MDD to create strain in channel—Metal oxide semiconductor transistor e.g. NMOS transistor has stress inducing regions on opposite of channel, such that distance between source and drain extension regions is greater than distance between stress inducing regions. Inventor: Chidambaram, P R
U.S. Pat. No. 6,323,525: MISFET semiconductor device having relative impurity concentration levels between layers—MISFET element for semiconductor IC—has source and drain areas formed from n+ type semiconductor layer and n− type semiconductor layer—Inventor: Noguchi, Mitsuhiro
US20050082522A1: Strained channel transistor formation—Transistor comprises strained channel region formed of first material and being intermediate source region and drain region Inventor: Huang, Yi-Chun;